ABSTRACT
Research into the co-ordination of bimanual movements has been dominated by the use of static interceptive actions such as manual aiming (e.g. Schmidt, Zelaznik, Hawkins, Frank and Quinn, 1979; Marteniuk and MacKenzie, 1980; Sherwood, 1994) and rhythmical tapping tasks (e.g. Kelso, 1984; Heuer, 1985). There has been limited work on the co-ordination of dynamic interceptive actions such as two-handed catching. Two contrasting explanations of bimanual co-ordination receiving considerable attention in the past are those proposed by Kelso, Southard, and Goodman (e.g. 1979), and Marteniuk and MacKenzie (e.g. 1980). Considerable debate still exists over the underlying mechanism(s) responsible for interlimb co-ordination. The critical issue concerns whether the brain specifies the states of individual muscles separately in each limb or whether the activity of muscle groups across limbs is co-ordinated as part of one functional structure. Marteniuk and colleagues proposed a neural cross-talk model emphasising the role of a symbolic movement representation within the central nervous system (CNS) (see for example, Cohen, 1970; 1971; Marteniuk and MacKenzie, 1980; Marteniuk, MacKenzie and Baba, 1984). It was suggested that temporal and spatial outcomes of bimanual movements are a function of neural cross-talk between motor command centres. It was argued that neural cross-talk could occur at cortical and/or subcortical levels of the CNS via the descending contralateral/ipsilateral neural pathways. Kelso and colleagues (1979; 1983) proposed an alternative model of bimanual co-ordination to argue that the brain sends signals to functional muscle groupings superimposed across the two limbs. Their data demonstrating high levels of interlimb synchrony have been interpreted as support for the idea of actions being controlled via co-ordinative structures (Turvey, 1977), proposed as an answer to the degrees of freedom problem (Bernstein, 1967).
